1. Field of the Invention
The present invention relates to a defroster of a refrigerant circuit that uses a so-called internal intermediate pressure type two-stage compression rotary compressor, and a rotary compressor used in the refrigerant circuit.
2. Description of the Related Art
In a conventional refrigerant circuit of the aforesaid type, especially in the case of a refrigerant circuit using an internal intermediate pressure type two-stage compression rotary compressor, a refrigerant gas is introduced into a low-pressure chamber of a cylinder through a suction port of a first rotary compressing unit of the rotary compressor, and compressed into an intermediate pressure by a roller and a vane, then discharged from a high-pressure chamber of a cylinder into a hermetic vessel through the intermediary of a discharge port and a discharge muffling chamber. Further, the refrigerant gas of the intermediate pressure in the hermetic vessel is introduced into the low-pressure chamber of the cylinder through the suction port of a second rotary compressing unit, subjected to the second-stage compression by the roller and the vane to become a hot, high-pressure refrigerant gas, and introduced from the high-pressure chamber into a radiator of a gas cooler or the like constituting a refrigerant circuit through the intermediary of the discharge port and the discharge muffling chamber. In the radiator, the hot, high-pressure refrigerant gas radiates heat to effect heating action, and it is throttled by an expansion valve or a decompressor before it enters an evaporator where it absorbs heat to evaporate. After that, the cycle that begins with the suction into the first rotary compressing unit is repeated.
If a refrigerant exhibiting a large difference between high and low pressures, such as carbon dioxide (CO2), which is an example of carbonic acid gases, is used with such a rotary compressor, the pressure of the discharged refrigerant reaches 12 MPaG in the second rotary compressing unit wherein it obtained a high pressure, while the pressure thereof goes down to 8 MPaG in the first rotary compressing unit at a lower stage end to provide the intermediate pressure in the hermetic vessel. The suction pressure of the first rotary compressing unit is approximately 4 MPaG.
In the refrigerant circuit using such an internal intermediate pressure type two-stage compression rotary compressor, an evaporator develops frost, and the frost therefore has to be removed. To defrost the evaporator, if a hot refrigerant gas discharged from the second rotary compressing unit is supplied to the evaporator without reducing the pressure thereof by the decompressor (the hot refrigerant gas may be directly supplied to the evaporator or may be passed through the expansion valve or the decompressor without being decompressed therein (with the expansion valve fully open)), the suction pressure of the first rotary compressing unit rises, causing the discharging pressure (intermediate pressure) of the first rotary compressing unit to rise accordingly.
The refrigerant is introduced into the second rotary compressing unit and discharged, while it is not decompressed in the expansion valve. As a result, the discharging pressure of the second rotary compressing unit becomes equal to the suction pressure of the first rotary compressing unit. This leads to the reversion of the discharge pressure (high pressure) and the suction pressure (intermediate pressure) of the second rotary compressing unit.
The pressure reversion mentioned above can be prevented by eliminating the difference between the discharging pressure and the suction pressure in the second rotary compressing unit. This can be accomplished by letting the refrigerant gas of an intermediate pressure discharged from the first rotary compressing unit enter the evaporator without decompressing it, in addition to the refrigerant gas discharged from the second rotary compressing unit.
The vane is subjected to the urging force by a coil spring (a spring member) and the discharging pressure of the second rotary compressing unit as a back pressure. The vane is pressed against the roller mainly by the urging force of the coil spring (spring member) when the rotary compressor starts running, and by the back pressure after it starts running. However, if the refrigerant gases discharged from the first and second rotary compressing units are introduced into the evaporator to defrost the evaporator as described above, the back pressure for pressing the vane against the roller disappears. This leads to a problem in that only the urging force of the coil spring (spring member) remains, and causes the vane to detach from the roller, known as xe2x80x9cvane jumpxe2x80x9d, contributing to deteriorated durability.
The vane attached to the rotary compressor is movably inserted in a slot provided in the radial direction of the cylinder, the vane being movably inserted in the radial direction of the cylinder. At the rear end of the vane (the end adjacent to the hermetic vessel), a spring hole (housing section) that opens to the outside of the cylinder is provided. The coil spring (spring member) is inserted in the spring hole, an O-ring is inserted in the spring hole from an opening in the outside of the cylinder, and the spring hole is closed by a plug (slippage stopper) thereby to prevent the spring from jumping out.
In this case, the plug is subjected to a force in the direction in which the plug is pushed out of the spring hole by the eccentric rotation of the roller. Especially in the case of an internal intermediate pressure type rotary compressor, the pressure in the hermetic vessel becomes lower than the pressure in the cylinder of the second rotary compressing unit. Hence, the difference between the inside pressure and the outside pressure of the cylinder also tends to push the plug out. For this reason, the plug has conventionally been press-fitted into the spring hole to secure it to the cylinder. This, however, has been causing a problem in that the press-fitting deforms the cylinder such that it expands, with a consequent gap between the cylinder and a supporting member or bearing that closes the opening surface of the cylinder. Thus, the air-tightness in the cylinder cannot be secured, resulting in degraded performance of the cylinder.
To solve the problem, if, for example, the outside diameter of the plug is set to be smaller than the inside diameter of the spring hole so as to prevent the deformation of the cylinder (in this case, it is necessary to make an arrangement to prevent the plug from coming off into the hermetic vessel), then the plug would be pushed toward the spring due to the intermediate pressure in the hermetic vessel when the rotary compressor stops and the pressure at the high pressure end in the cylinder drops. As a result, the spring may be crushed and the operation may fail.
As another alternative solution, if, for example, the outside diameter of the plug is set to be larger than the inside diameter of the spring hole to an extent that would not cause the cylinder to deform, then it would be difficult to determine how far the plug should be inserted into the spring hole.
Accordingly, the present invention has been made toward solving the technological problems with the prior art, and it is an object of the invention to restrain a vane from pumping when an evaporator is defrosted in a refrigerant circuit using a so-called internal intermediate pressure type two-stage compression rotary compressor, and to provide a rotary compressor capable of restraining the vane from jumping.
It is another object of the present invention to provide a rotary compressor that has a plug provided at a predetermined position to prevent a spring for urging a vane from coming off, and is capable of preventing the deformation of a cylinder.
To these ends, according one aspect of the present invention, there is provided a defroster in a refrigerant circuit including: a rotary compressor that has a hermetic vessel housing an electromotive unit and first and second rotary compressing units driven by the electromotive unit, discharges a refrigerant gas that has been compressed by the first rotary compressing unit into the hermetic vessel, and further compresses the discharged, intermediate-pressure refrigerant gas by the second rotary compressing unit; a gas cooler into which the refrigerant discharged from the second rotary compressing unit of the rotary compressor flows; a decompressor connected to the outlet end of the gas cooler; and an evaporator connected to the outlet end of the decompressor, the refrigerant from the evaporator being compressed by the first rotary compressing unit, the rotary compressor comprising a cylinder constituting the second rotary compressing unit and a roller that is fitted to an eccentric portion formed in a rotary shaft of the electromotive unit and eccentrically rotates in the cylinder, a vane abutted against the roller to partition the interior of the cylinder into a low-pressure chamber and a high-pressure chamber, a spring for constantly urging the vane toward the roller, and a back pressure chamber for applying the discharge pressure of the second rotary compressing unit to the vane as a back pressure, wherein in order to defrost the evaporator, the defroster introduces the refrigerant gas discharged from the second rotary compressing unit into the evaporator without being decompressed by the decompressor, also introduces the refrigerant gas discharged from the first rotary compressing unit into the evaporator, drives the electromotive unit of the rotary compressor at a predetermined number of revolutions, and sets the inertial force of the vane at the predetermined number of revolutions to be smaller than the urging force of the spring.
According to another aspect of the present invention, there is provided a defroster of a refrigerant circuit including: a rotary compressor that has a hermetic vessel housing an electromotive unit and first and second rotary compressing units driven by the electromotive unit, discharges a refrigerant gas that has been compressed by the first rotary compressing unit into the hermetic vessel, and further compresses the discharged, intermediate-pressure refrigerant gas by the second rotary compressing unit; a gas cooler into which the refrigerant discharged from the second rotary compressing unit of the rotary compressor flows; a decompressor connected to the outlet end of the gas cooler; and an evaporator connected to the outlet end of the decompressor, the refrigerant from the evaporator being compressed by the first rotary compressing unit, the rotary compressor comprising a cylinder constituting the second rotary compressing unit, a roller that is fitted to an eccentric portion formed in a rotary shaft of the electromotive unit and eccentrically rotates in the cylinder, a vane abutted against the roller to partition the interior of the cylinder into a low-pressure chamber and a high-pressure chamber, a spring for constantly urging the vane toward the roller, and a back pressure chamber for applying the discharge pressure of the second rotary compressing unit to the vane as a back pressure, a defroster of the refrigerant circuit that, in order to defrost the evaporator, introduces the refrigerant gas discharged from the second rotary compressing unit into the evaporator without being decompressed by the decompressor, also introduces the refrigerant gas discharged from the first rotary compressing unit into the evaporator, and drives the electromotive unit of the rotary compressor at a number of revolutions at which the inertial force of the vane is smaller than the urging force of the spring.
According to still another aspect of the present invention, there is provided a rotary compressor that includes a hermetic vessel housing an electromotive unit and first and second rotary compressing units driven by the electromotive unit, and is used in a refrigerant circuit that discharges a refrigerant gas that has been compressed by the first rotary compressing unit into the hermetic vessel, and further compresses the discharged, intermediate-pressure refrigerant gas by the second rotary compressing unit, and includes a gas cooler into which the refrigerant discharged from the second rotary compressing unit of the rotary compressor flows, a decompressor connected to the outlet end of the gas cooler, and an evaporator connected to the outlet end of the decompressor, and drives the electromotive unit at a predetermined number of revolutions and introduces the refrigerant gases discharged from the first and second rotary compressing units into the evaporator without decompressing the refrigerant gas when defrosting the evaporator, the rotary compressor including a cylinder for constituting the second rotary compressing unit and a roller that is fitted to an eccentric portion formed in a rotary shaft of the electromotive unit and eccentrically rotates in the cylinder, a vane abutted against the roller to partition the interior of the cylinder into a low-pressure chamber and a high-pressure chamber, a spring for constantly urging the vane toward the roller, and a back pressure chamber for applying the discharge pressure of the second rotary compressing unit to the vane as a back pressure, the inertial force of the vane at the number of revolutions of the electromotive unit when defrosting the evaporator being weaker than the urging force of the spring.
With this arrangement, when the evaporator is defrosted, the refrigerant gas discharged from the second rotary compressing unit and the refrigerant gas discharged from the first rotary compressing unit are introduced into the evaporator without decompressing them. Thus, the inconvenience can be prevented in which the discharge pressure and the suction pressure of the second rotary compressing unit of the rotary compressor are reversed when the evaporator is defrosted.
Especially because the inertial force of the vane at the number of revolutions of the electromotive unit in the evaporator defrosting mode becomes smaller than the urging force of the spring, the inconvenience in which the vane jumps in the second rotary compressing unit in the evaporator defrosting mode can be also avoided. This makes it possible to defrost the evaporator without adversely affecting the durability of the rotary compressor.
According to a further aspect of the present invention, there is provided a rotary compressor that includes a hermetic vessel housing an electromotive unit and first and second rotary compressing units driven by the electromotive unit, and discharges a gas that has been compressed by the first rotary compressing unit into the hermetic vessel, and further compresses the discharged, intermediate-pressure gas by the second rotary compressing unit, the rotary compressor including a cylinder for constituting the second rotary compressing unit and a roller that is fitted to an eccentric portion formed in a rotary shaft of the electromotive unit and eccentrically rotates in the cylinder, a vane abutted against the roller to partition the interior of the cylinder into a low-pressure chamber and a high-pressure chamber, a spring for constantly urging the vane toward the roller, a housing portion for the spring that is formed in the cylinder and opens toward the vane and the hermetic vessel, and a plug provided in the housing portion so that it is positioned at the hermetic vessel end of the spring to seal the housing portion, a retaining portion against which the plug abuts at a predetermined position being formed on the inner wall of the housing portion that is positioned at the spring end of the plug.
Preferably, the outside diameter of the plug of the rotary compressor is set to be larger than the inside diameter of the housing portion to an extent that will not cause the cylinder to deform when the plug is inserted in the housing portion.
Preferably, the outside diameter of the plug of the rotary compressor is set to be smaller than the inside diameter of the housing portion.
Preferably, the retaining portion of the rotary compressor is formed such that the diameter of the inner peripheral wall of the housing portion is reduced so as to form a step on the inner peripheral wall.
Thus, the rotary compressor in accordance with the present invention includes a hermetic vessel housing an electromotive unit and first and second rotary compressing units driven by the electromotive unit, and discharges a gas that has been compressed by the first rotary compressing unit into the hermetic vessel, and further compresses the discharged, intermediate-pressure gas by the second rotary compressing unit, the rotary compressor including a cylinder for constituting the second rotary compressing unit and a roller that is fitted to an eccentric portion formed in a rotary shaft of the electromotive unit and eccentrically rotates in the cylinder, a vane abutted against the roller to partition the interior of the cylinder into a low-pressure chamber and a high-pressure chamber, a spring for constantly urging the vane toward the roller, a housing portion for the spring that is formed in the cylinder and opens toward the vane and the hermetic vessel, and a plug provided in the housing portion so that it is positioned at the hermetic vessel end of the spring to seal the housing portion, a retaining portion against which the plug abuts at a predetermined position being formed on the inner wall of the housing portion that is positioned at the spring end of the plug. Thus, the retaining portion prevents the plug from moving further toward the spring.
With this arrangement, the plug can be retained at a predetermined position. Accordingly, if, for example, the outside diameter of the plug is set to be larger than the inside diameter of the housing portion to an extent that will not cause the cylinder to deform when the plug is inserted in the housing portion, then the plug can be positioned when it is press-fitted into the housing portion while preventing the cylinder from deforming due to the insertion of the plug. This improves the ease of the installation of the plug.
If, for example, the outside diameter of the plug is set to be smaller than the inside diameter of the housing portion, then it is possible to prevent the plug from being inconveniently pushed toward the spring by the intermediate pressure in the hermetic vessel when the rotary compressor stops.
Preferably, the retaining portion is formed by reducing the diameter of the inner peripheral wall of the housing portion to form a stepped portion. This permits the retaining portion to be easily formed in the housing portion of the cylinder, resulting in reduced production cost.
Preferably, the rotary compressing units in the defroster or the rotary compressor of a refrigerant circuit in accordance with the present invention effect compression by using CO2 gas as the refrigerant.
Preferably, the defroster or the rotary compressor of the refrigerant circuit in accordance with the present invention generates warm water by using the heat radiated from the gas cooler.
Thus, marked advantages are obtained especially when the CO2 gas is used as the refrigerant. When warm water is produced by making use of the heat from the gas cooler, it becomes possible to convey the heat of the warm water of the gas cooler to the evaporator by the refrigerant. This provides an additional advantage in that the evaporator can be defrosted more quickly.